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β-glucosidase is a key component of cellulase for its function in hydrolyzing cellobiose to glucose in the final step of cellulose degradation. The high-level expression of β-glucosidase is essential for cellulose conversion. Aspergillus niger ATCC 20611 has the potential for efficient protein expression because of its ability to secret enzymes for the industrial production of fructooligosaccharides, but it lacks robust promoters for high-level protein expression. Here, the development of A. niger 20611 as a powerful protein expression system exploited the conserved constitutive promoter Pgpd1 of the glyceraldehyde-3-phosphate dehydrogenase-encoding gene from Trichoerma reesei to drive the expression of the enhanced green fluorescent protein in A. niger ATCC 20611. The mycelium of the transformant AGE9 exhibited intense fluorescence. Then, the promotor Pgpd1 was used to drive the expression of β-glucosidase and the enzyme activity of transformants AGB1 and AGB33 were 1.02 and 0.51 U/mL, respectively. These results demonstrate that the promotor Pgpd1 from T. reesei was applicable for A. niger ATCC 20611. Furthermore, the T. reesei-specific robust promoter Pcdna1 was used to drive the expression of β-glucosidase. The β-glucosidase exhibited a high-level expression with a yield of 15.2 U/mL, which was over 13.9 times higher than that driven by the promoter Pgpd1. The β-glucosidase was thermally stable and accounted for 85% of the total extracellular proteins. Subsequently, the fermentation broth including β-glucosidase was directly added to the cellulase mixture of T. reesei for saccharification of the acid-treated corncob residues and the delignified corncob residues, which increased the saccharification efficiency by 26.21% and 29.51%, respectively. Thus, β-glucosidase exhibited a high level of expression in A. niger ATCC 20611 and enhanced cellulose degradation by addition in vitro. In addition, the robust promoter Pcdna1 of T. reesei could drive the high-level expression of protein in A. niger ATCC 20611. These results demonstrate that the promoters in filamentous fungi could be employed across species in A. niger ATCC 20611 and further facilitated the efficient expression of β-glucosidase to optimize cellulases for efficient cellulose transformation. Full article

Kefir beverage (KB) is a fermented milk initiated by kefir grains rich with starter probiotics. The KB produced in this study seemed to contain many chemical compounds elucidated by gas chromatography–mass spectrometry (GC-MS) and IR spectra. These compounds could be classified into different chemical groups such as alcohols, phenols, esters, fatty esters, unsaturated fatty esters, steroids, polyalkenes, heterocyclic compounds and aromatic aldehydes. Both KB and neutralized kefir beverage (NKB) inhibited some pathogenic bacteria including Escherichia coli ATCC11229 (E. coli), Listeria monocytogenes ATCC 4957 (L. monocytogenes), Bacillus cereus ATCC 14579 (B. cereus), Salmonella typhimurium ATCC 14028 (Sal. typhimurium) as well as some tested fungal strains such as Aspergillus flavus ATCC 16872 (A. flavus) and Aspergillus niger ATCC 20611 (A. niger), but the inhibitory activity of KB was more powerful than that obtained by NKB. It also appeared to contain four lactic acid bacteria species, one acetic acid bacterium and two yeast species. Finally, the KB inhibited distinctively both S. aureus and Sal. typhimurium bacteria in a brain heart infusion broth and in some Egyptian fruit juices, including those made with apples, guava, strawberries and tomatoes. Full article